The present invention relates to new macrolide derivatives, in particular new tylosin derivatives; a pharmaceutical or veterinary composition comprising any of the derivatives; a method for preparation thereof; a method for treating and/or preventing bacterial infections in an animal, wherein the method comprises administering any of the derivatives or the composition; and a use of the derivatives for the manufacture of medicaments for treating and/or preventing bacterial infections in an animal.
Macrolides in generally have a chemical structure of 12-, 14- or 16-membered macrocyclic group (aglycone) substituted with 1 to 3 substituents such as neutral sugars, deoxy sugars or amino sugars. Macrolides have a wide spectrum of antibacterial activities against for example Pneumococcus spp, Streptococcus spp, Hemophilus influenzae, Staphylococcus aureus, Actinobacillus spp, Pasteurella spp and atypical pathogen such as Mycoplasma, Legionella or Chlamydia that is resistant to other drugs. Consequently, macrolides have been used for the treatment of among others a variety of respiratory tract infections. A variety of macrolides have been discovered or synthesized until now, typically including tylosin represented by the following formula:

Tylosin has been used for the treatment of infections of Gram-positive bacterium and Mycoplasma in farm animals.
In order to further expand the spectrum of tylosin and to improve its oral bioavailability, a number of tylosin derivatives have been tested. Examples of such tylosin derivatives typically include among others tilmicosin and tulathromycin (tulathromycin belongs to a different class of compounds) represented by the following formulae, respectively:

Tilmicosin and tulathromycin are useful for the treatment of pasteurellosis caused by Gram negative bacillus such as Pasteurella or Mannheimia. They are the most commonly used and important antibiotics in farm animals.
However, new antibiotics are inextricably associated with the emergence of resistant bacteria. Accordingly, there is still a need to provide new antibiotics.
The backgrounds may be reflected in the following patent and Non-patent References: